I had the same problem and posted about it last night. Didn't get much of a response, but I changed to a seperate power point and still didn't happen. Seems to be with powered External Hard Drives but not all are causing the problem. It only happens when the power is ON at the wall. If power is off at the wall, the interference stops. So it is powered interference through the power supply I imagine. I had two of the same brand, RITMO and both did the same thing. Hard Drive used is IDE not SATA not that it should make much difference. Might try getting a different External 3.5" unit.

The problem only occurs when the usb lead is plugged into the back of the Wii. There is no problem when both Wii and USBHD are powered on together. The interference only appears as soon as the usb lead is plugged in.

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Have tried a different power supply and the problem is the same.

Have tried different plug sockets and still no change.

The problem only occurs when the usb lead is plugged into the back of the Wii. There is no problem when both Wii and USBHD are powered on together. The interference only appears as soon as the usb lead is plugged in.

I had the exact same problem using a 40gb HDD from an old PC and a cheap ebay style IDE to USB adaptor with power adaptor. The interference would occur as soon as you plug in the usb. Also it was connected to a separate powerpoint.

I have since bought a western digital usb powered 320gb HDD and don't have the problem.

I concur. I had a cheapo USB Enclosure with LED lights and that caused major wavy lines. I then took the same drive and put it in a slightly better enclosure with no lights and the problem is 98% gone. I can live with the occasional 2% annoyance. The above numbers are estimates - they do not reflect actual real world statistics LOL!